Introduction to LED Solid-state Lighting and the Optical Design

Microsoft PowerPoint - -SUN-111215 2011/12/15
Tel:+886-3-4276240, Fax:+886-3-4252897 http://www.dop.ncu.edu.tw/, Email : [email protected]
Introduction to LED Solid-state Lighting and the Optical Design
2
History of DOP
1982
2006
3

LED Solid-state LightingProjection Display3D Holographic DisplayHuman Factors OpticsColor
TechnologyPhotometryLaser DisplayGlareVision…
Since Aug. 1st, 2008
LED Industry in NCU
5
Motives of LED Lighting
Energy Efficient LEDs up to 90% less energy
Long Life LEDs last up to 100,000 hrs compared to 1000 for typical
incandescent bulbs. Vivid Colors
LEDs give pure saturated colors with up to 130% more color gamut compared to standard NTSC specifications. High Reliability
LEDs ae solid state devices, no moving parts, no glass and no filaments to break. Environmentally Friendly
LEDs contain no mercury, and are less disposal waste in the environment owing to long life. Increased Safety
LEDs turn on faster, providing quicker response in applications like automotive brake lights. Multiple Applications
6
Illumination Requirement
Progress in LED’s Efficiency
@ 20 mA
@ 350 mA
Lu m
in ou
s E
ffi ci
en cy
(l m
LED’s World record
LED 2009
Lighting Agriculture
Material Chip
Color
PackagePhosphor
JI Chyi, CC Chen, CY Liu, RS Liu, JY Chang, MJ Wu, TY Chung, TH Yang, CC SUN
CC SUN, TH Yang, TY Chung, YC Chen, CY Liu, KY Lai, G Zissis, SY Chen, CH Chang, CC Chen, JI Chyi
Display
Thermal Management
Thermal Conductivity
12
Junction Temperature
Tj = Rja × P + Ta Junction Temperature = Ambient Temperature+ Thermal Resistance (Rja) × Input Power (W)
T
T
T
T
junction
slug
board
ambient
Die
Slug
High-power LED Package
World’s Brightest RGB LED Array
Flux : 13,300 lm, LED No. : 270 R/G/B, Flux Density : 677 lm/in2 ,CT : 3300- 6500K, R : 4,600 lm / 210W, G : 7,600 lm / 320W, B : 1,100 lm / 330W
Flux : 28000 lm, LED No. : 1120, Power : 1400 W, CT : 5500K, CRI : 80
From Lamina
World’s Brightest LED Lamp
60 lm/W @ 4W
58 lm/W @ 8W
Color Issues
Correlated Color Temperature
Color Rendering Index
19
RGB Color Mixing
-- High Color Gamut
-- Excellent Color Tuning
20
Competition in Lighting
21
Phosphor - Blue Chip
make an LED to perform consistent color performance
enable small spatial CCT variation
improve the yield rate of package
optimize the luminous efficiency
Modeling Procedure
Blue Yellow
phosphor plate
Absorption coefficient
phosphor plate
phosphor plate
Scattering modeling Scattering modeling
Ref : C. C. Sun, C. Y. Chen, H. Y. He, C. C. Chen, W. T. Chien, T. X. Lee and T. H. Yang, “Modeling the radiation pattern of LEDs,” Optics Express 16, 20060-20066 (2008).
23
Color Coordinate
0.18
0.20
0.22
0.24
0.26
0.28
w/o Lens
w/o Lens
with Lens
with Lens
Ref : C. C. Sun, C. Y. Chen, H. Y. He, C. C. Chen, W. T. Chien, T. X. Lee and T. H. Yang, “Modeling the radiation pattern of LEDs,” Optics Express 16, 20060- 20066 (2008).
24
Verification with Real Package
Δx=+0.007 Δy=-0.002
Δx=-0.003 Δy= +0.004
Δx=+0.004 Δy= 0.000
Ref : C. C. Sun, C. Y. Chen, H. Y. He, C. C. Chen, W. T. Chien, T. X. Lee and T. H. Yang, “Modeling the radiation pattern of LEDs,” Optics Express 16, 20060- 20066 (2008).
25
Spatial CCT Uniformity
A good emitter generates consistent CCT for all viewing angles
-100 -80 -60 -40 -20 0 20 40 60 80 100 0
1000 2000 3000 4000 5000 6000 7000 8000 9000
10000 11000
C C
T (K
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
-100 -80 -60 -40 -20 0 20 40 60 80 100 0
1000
2000
3000
4000
5000
6000
7000
8000
9000
Delta CCT: 2,956 K
-100 -80 -60 -40 -20 0 20 40 60 80 100 0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
11000
Ref: ANSI C78.377-2008
44 K 71K
World-leading Color Performance
RGB Color Mixing
29
BLU

Polarizer
AR AG ABBacklight
–
0
1000
2000
3000
4000
5000
380 420 460 500 540 580 620 660 700 740 780
nm
m
Display
0
2000
4000
6000
8000
10000
12000
14000
16000
380 420 460 500 540 580 620 660 700 740 780
nm
RGB LED
CCFL backlight = 70.51 % NTSC
RGB LED BLM of NCU IOS CCFL BLM
Optics of Solid-State Lighting Lab., DOP , NCU
33
34
35
LED
2D vs. 3D

CG : 72% NTSC

Motion blur reduction
Progressive lighting of the BLU of the image frames can reduce motion blur.
Conventional Scanning BLU
Cost Issue
But more-function requirement of LED BLU is not cost-effective
Ref : Samsung Electronics
New Technology by NCU
CG : 122.05 % NTSC
CG : 121.99 % NTSC
for LCTV with color filter
The new technology has been ready to transfer to worldwide industry.
41
Optical Issues
Optical Issues in LED SSL
Zero-order Optics
Lighting vs. Imaging
Software – Monte Carlo Ray Tracing
ASAP – Breault Research Organization, Inc.
http://www.breault.com/
http://www.opticalres.com/
http://www.lambdares.com/
Optical Model
Fig. form ASAP2005 Documentation
LED : Complicated Light Source
Verification of an LED Model
At What Distance ?
Position-dependent ray vector measurement required
Far Field ?
Far-filed pattern is an angular pattern
48
Mid-field Region
Mid Field
Scalar field, the pattern varies from one to another plane, Most optical elements are in this region.
Vector field
Angular field
Ref : C. C. Sun, T. X. Lee, S. H. Ma Y. L. Lee and S. M. Huang, Optics Letters 31, 2193-2195 (2006).
49
1-D Light Pattern (cd)
Chip Parameters
Measurement vs. Simulation
1 cm
-90 -75 -60 -45 -30 -15 0 15 30 45 60 75 90
0.0
0.2
0.4
0.6
0.8
1.0
Measurement Simulation
Ref .: W. T. Chien, C. C. Sun, and I. Moreno, “ Precise optical model of multi-chip white LEDs,” Optics Express 15, 7572- 7577 (2007).
52
3 cm
-90 -75 -60 -45 -30 -15 0 15 30 45 60 75 90
0.0
0.2
0.4
0.6
0.8
1.0
5 cm
-90 -75 -60 -45 -30 -15 0 15 30 45 60 75 90
0.0
0.2
0.4
0.6
0.8
1.0
7 cm
-90 -75 -60 -45 -30 -15 0 15 30 45 60 75 90
0.0
0.2
0.4
0.6
0.8
1.0
10 cm
-90 -75 -60 -45 -30 -15 0 15 30 45 60 75 90
0.0
0.2
0.4
0.6
0.8
1.0
30 cm
-90 -75 -60 -45 -30 -15 0 15 30 45 60 75 90
0.0
0.2
0.4
0.6
0.8
1.0
Design of Multi-chip white LED
Real sample Optical model
Photon Recycling
Efficiency Enhancement – Photon Recycling

…
DBEF : Photon-recycling
Optics Approaches in LED SSL
Zero-level Optics
Light Extraction : Roughening
By introducing a 2-D periodic structure in an interface between two materials with large refractive index difference
63
Surface Texture in Thin-GaN
Reference: T. Fujii, Y. Gao, R. Sharma, E. L. Hu, S. P. Danbaars, and S. Nakamura, “Increase in the extraction efficiency of GaN-base light emitting diodes via surface roughening,” App. Phys. Lett. 84, 855, (2004)
64
Three Types of LED
Light Extraction from Die
MQW p-GaN
PC structure of surface texture
66
LEE by Cavity Photon-recycling
Ref. : Optics Communications 284, 4862-4868 (2011).
Ref. : Optics Express 15, 6670-6676 (2007).
67
Directionality Enhancement through Photon-recycling
dAS dΩ
2 cos S aperture
. . 2cos Lamb
εθ= Φ = Ω =∫∫
Etendue : a Geometric Factor
Review : Directionality Enhancement
RefProc. of SPIE Vol. 7518, 75180A, 2009
70
Squeeze Etendue by PC Structure
Photonic Crystal (Diffraction Structure)
Original case : Light extracted from the die
Ideal case : 100% light extraction (total flux by the active layer)
through PC Structure
71
Angular Flux Utilization (AFU)
Larger AFU means more flux in a certain light cone but not for smaller etendue.
Lager LEE means less lights absorbed in the LED so less heat is generated.
72
15°439.1% 30°423.6% 60°404.3%
15°142.4% 30°190.5% 60°263.3%
15°366.5% 30°362.6% 60°435.7%
15°259.5% 30°312.4% 60°464.1%
15°107.4% 30°114.0% 60°116.6%
15°252.6% 30°253.6% 60°273.3%
15°305.4% 30°305.8% 60°370.0%
100%
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Lighting Cavity through Photon-recycling
LED Lighting with Low Glare
Better quality of LED illumination :
• Low-glare illumination • Tunable planar light source • Luminance & Color Uniformity
Uniformity vs. Efficiency
High-efficiency Cavity with PR
Optical Efficiency (Single Diffuser)
T
( )
Rb 2 x R2
………
77
Diffuser plate #1 T1 : one-shot transmittance
R1 : one-shotreflectance T1 + R1 < 1 (Absorption)
Optical efficiency :
R2 : one-shot reflectance T2 + R2 < 1 (Absorption)
T12
Rb x R12 2
2
Ref. : Optics Express 18, 6137-6148 (2010).
78
Volume-scatter Diffusers
Side Walls with High Reflectivity
Cross section Random rough surface
High reflective sliver-coating sheet
I. Sliver Scatter sheet (R=82%)
II. White Scatter sheet (R=86%)
The high reflective sheet and white scatter sheet are usually used in BL !
80
Cavity Efficiency
63.4% (60.4)
69.4% (69.8)
70.5% (72.9%)
2 diffusers (E2)
78.9% (79.2%)D55
80.9% (84.3%)D60
82.8% (86%)D70
1 diffuser (E1)
* Cavity size is 9 × 9 ×4 cm3. * 2 Diffusers : One is located on top of the cavity, the other is located at half of the height. * Light source : White LED.
Ref. Optics Express 18, 6137-6148 (2010).
81
RR TE
0.70 0.75 0.80 0.85 0.90 0.95 1.00 0.70
0.75
0.80
0.85
0.90
0.95
1.00
Surface-structured Diffusers 62.6μm
20080504_03_180sec_g14_50x_3D
83
Beam Shaping
5° 30° 80° 50°x10°
20081031_lens array_case1 20081031_lens array_case1
Optical Cavity in High-photon-recycle Rate
R=95%
What is True Efficiency ?
Improvement of Lighting
Source: http://www.cpre.org.uk/filegrab/night-blight-report-32pp.pdf?ref=1759
Original Full Cutoff
Useful light
Sky glow
Wasted Energy
Glare zone
Direct glare
Spill light
Light trespass
Source: NLPIP
?
89

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Introduction to LED Solid-state Lighting and the Optical Design

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